Acrylate-based polymers and their use as flameproofing agents

ABSTRACT

A polymer having as a component thereof a moiety corresponding to a monomer having the following formula ##STR1## WHEREIN N = 0 OR 1, X is bromine, chlorine or a mixture thereof and R represents hyrogen or methyl, a method of preparing the same and the use of such a polymer, including a copolymer thereof in a plastic composition containing a normally flammable plastic.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to novel polymers and copolymers based onpentabromobenzyl esters and tetrabromoxylylene diesters of the formula##STR2## WHEREIN N = 0 OR 1, X IS BROMINE, CHLORINE OR A MIXTURE THEREOFAND R is hydrogen or methyl. This invention relates to a method ofpreparing such polymers and copolymers and the use of such polymers andcopolymers in normally flammable plastic compositions.

Discussion of the Prior Art

It is common practice to render thermoplastics fire-resistant orincombustible by adding flame-inhibiting substances to them when theyare being prepared or fabricated. As a rule, substances are used forthis purpose which have no chemical relationship to the organic polymersconstituting the thermoplastics, such as, for example, halogen, ororganic or inorganic substances of low molecular weight containingphosphorus and nitrogen, or mixtures of such substances with metaloxides which sometimes interact to enhance the flame-inhibiting action.Such additives to thermoplastics always produce side effects in additionto their flame-inhibiting action, which as a rule are undesirablebecause they impair the characteristic properties of the thermoplasticsand limit their usefulness. Thus all flame-inhibiting substances whichare added in powder form to the thermoplastic and remain in powder formtherein or, when they cool after being melted and mixed, separate againas an independent phase, produce not only the desired flame-inhibitingeffect, but also act as fillers which modify the mechanical propertiesof the thermoplastics, as a rule by embrittling them, and reduce theirelongation at rupture and their impact strength.

Additives which melt upon incorporation into thermoplastics are a sourceof other disadvantages. Often their vapor pressures are too low at thetemperatures at which they are to be fabricated, or they decompose atthose temperatures. In nearly all cases, the flame-proofing agentsincorporated have a more or less great tendency to diffuse back out ofthe plastic; this "chalking out" gradually destroys the fire-resistanceof the plastics, and plastics which have been flame-proofed in thismanner cannot be used in a great number of applications, such as theconstruction of electrical appliances for example.

Attempts have been made to make plastics of this kind fire-resistant,and a great number of substances are offered on the market for additionto the plastics for the purpose of making them fire-retardant orflameproof. Such substances are, for example, metal compounds of zinc,lead, iron, antimony and aluminum, such as oxides, borates, phosphatesand other salts of weak acids, and also chemicals of organic chemistrycontaining in their molecules components which make them flameproof,such as nitrogen, phosphorus, sulfur, the halogens chlorine and bromine,or combinations thereof. Often mixtures of different substances whichenhance one another's flameproofing action are used.

However, the fire-retardant action of these substances is slight, sothat considerable amounts of them have to be added to achieve thedesired effect. Usually the addition of 12% and more is necessary. Sinceas a rule these additives are substances which are chemically foreign tothe plastics, such as, for example, metal salts or monomolecularchemical compounds, their addition has undesirable effects on thecharacteristics of the plastics which contain them. That is, theseadditions often act as fillers and thus have an embrittling effectoften, too, they are so poorly compatible with the plastics that theygradually diffuse out of the finished product resulting in a chalkycoating on the surface of the plastic mixture. If this chalking becomesapparent even at room temperature, this defect is all the moreundesirable in articles which are exposed to an elevated temperature inuse. In the case of sublimating flameproofing agents, the resistance ofthe plastics to fire diminishes, of course, as the flameproofing agentsublimates, so that in such cases lasting protection is not assured. Inthe electrical industry, plastic articles which chalk in the mannerdescribed are entirely unusable, since they can cause considerabletrouble in electrical apparatus or installations.

Another frequently observed deficiency in such flameproofing agents isan excessively low decomposition temperature, so that stabilizers mustbe added when they are incorporated into the plastic involved, and theseagain modify the properties of the mixture in an uncontrollable manner.

The problem thus arises of flameproofing plastics in such a manner as toavoid the above-described disadvantages and render them equal in theirgeneral characteristics to those which have not been flameproofed.

It has therefore become desirable to provide fire-retardant substanceswhich are chemically related to the plastic compositions in which theyare to be used. More especially, it has become desirable to provide aflame-retardant agent chemically related to such substances which has amelting point within the processing temperatures employed in fabricationof plastic molding in extrusion compositions into final articles. Moreespecially, it has become desirable to provide such a flame-retardantagent which has an exceptionally high quantity of combined bromine andchlorine content. Moreover, it has become desirable to provide such afire-retardant composition which is superior to known fire-retardantagents at the same bromine and chlorine content.

SUMMARY OF THE INVENTION

Broadly, this invention contemplates a polymer or copolymer having as acomponent thereof a moiety corresponding to a monomer having thefollowing formula: ##STR3## wherein n = 0 or 1, X is bromine, chlorineor a mixture thereof and R represents hydrogen or a methyl group.

In accordance with this invention it has been found that such polymersprovide excellent flame-proofing properties especially when incorporatedinto plastic compositions which are normally flammable. It has beenfound in accordance with the present invention that polymers andcopolymers containing a moiety corresponding to the monomers whoseformula is set above can be prepared quite readily by a radical, e.g.,free radical polymerization carried out in the presence of a radicalforming agent under radical polymerization conditions. Generally, theseconditions are those known and generally include a temperature of0°-150° C. Known radical forming agents can be employed to facilitatethe polymerization.

The unsaturated diesters of Formula 1 in which n = 0 can serve asmonomers, preferably the isomeric tetrabromoxylylenediacrylates, as wellas the isomeric tetrabromoxylylenedimethacrylates, or the mixturethereof, are those having the following formulae: ##STR4## wherein Rrepresents hydrogen or a methyl group and X represents bromine orchlorine. Other isomers are pentabromobenzylacrylate andpentachlorobenzylacrylate and the corresponding methacrylates.

Polymers and copolymers of this invention have if they are solublemolecular weights generally between 1·10³ and 10·10⁶ preferably between5·10³ and 5·10⁶. The molecular weight values given are thosedeterminable in accordance with the technique of Gel PermeationChromatography and Solution Viscosity as published in B. Vollmert,"Goundriss der mackromoleku laren Chemie."

The pentabromobenzylacrylates and methacrylates and thetetrabromoxylylenebisacrylates or bismethacrylates, as the case may be,are ordinarily the pure bromine substitution products, but there arealso usable monomers in whose preparation a portion of the bromine boundto the aromatic nucleus has been replaced by chlorine. The use of thesubstituent X takes this into account. The amount of chlorine generallywill not be more than one chlorine per molecule of the monomer, so thatthe following are to be written as the preferred monomer units,respectively: ##STR5##

The unsaturated esters of Formula I, the corresponding chlorinatedesters and methods for their preparation from alkali salts of acrylicand methacrylic acid and benzyl and xylylene chlorides brominated andchlorinated in the nucleus have recently become accessible.

They can be prepared in accordance with commonly owned Ser. No. 589,958filed Jan. 24, 1975, the disclosure of which is hereby incorporatedherein by reference. The compounds are produced by contacting an alkalisalt of

    R' - CH = C(R) - COOH

wherein R and R' independently represent hydrogen or methyl withtetrahalogenxylene chloride or xyxylene dichloride or pentabromobenzylchloride in a polar solvent. Compounds of such formulae can also beproduced by reacting acrylic or methacrylic acid in a polar solvent,e.g., in the presence of a polymerization inhibitor, e.g., hydroquinonewith an alkali metal hydroxide after which is added to the reactionmixture o- or m- tetrabromoxyxylene dichloride and an alcohol, e.g.,methyl glycol. The reaction mixture is heated at 50°-150° C. Theresultant alkali metal salt of the acid formed before the addition ofthe dichloride is present in a stoichiometric excess of 1 to 10 molepercent. This latter method is the invention of Georg Blumenfeld,Hermann Richtzenhain, Wilhelm Vogt and Norbert Vollkommer.

Also subject matter of the present patent application is a method ofpreparing the polymers and copolymers of the invention by procedures ofradical polymerization, e.g., free radical polymerization ofethylenically unsaturated compounds, which method is characterized inthat monomers of Formula 1 are polymerized, in some cases withadditional ethylenically unsaturated monomers.

Suitable comonomers for the preparation of the copolymers areethylenically unsaturated monomers which are radically copolymerizablewith the above-named acrulates and methacrylates, especially styrene,acrylonitrile, acrylic acid esters and methacrylic acid esters havingpreferably 1 to 6 carbon atoms in the alcohol radical, unsubstitutedxylylene acrylates and methacrylates as well as their chlorinesubstitution products as disclosed in said U.S. Ser. No. 589,958,butadiene and isoprene, fumaric and maleic acid and their anhydrides andpolyesters, and in some cases vinyl chloride vinylidene chloride andothers.

Generally speaking where copolymers are prepared the copolymer containscomponents whose moieties correspond to formula 1 in an amount ofbetween 1 and 99 weight percent, preferably 2 and 80 weight percent,based on the weight of the copolymer.

The polymerization of several comonomers to terpolymers is alsocontemplated, as for example the polymerization of several comonomers ofthe group of the acrylates and methacrylates, of acrylonitrile and ofthe above-named chlorinated acrylates and methacrylates, as well as thecommon copolymerization of several comonomers onto a support through agraft polymerization, such as for example modified ABS, MBS and highimpact strength polystyrene by the polymerization of suitable amounts ofacrylonitrile, methacrylates and/or styrene with the addition ofsubstances of Formula 1, onto a support of polybutadiene orpolyisoprene. Also contemplated is the cross-linking of unsaturatedpolyester resins which are prepared from a diol component such asethylene glycol or neopentyl glycol, an unsaturated acid component suchas fumaric or maleic acid, and, in some cases, an additionaldicarboxylic acid, and are then subjected to the copolymerization of theunsaturated reactive solvent such as styrene, for example, and of theunsaturated resin basis, with substances of Formula 1. Styrene andmethylmethacrylate, among others, are preferred.

Thermoplastic, un-crosslinked homopolymers are obtained when acrylicesters or methacrylic esters of structural Formula 1, wherein n = 1, aresubjected to polymerization, examples being pentabromobenzylacrylate orpentabromobenzylmethacrylate. The polymerization mechanism is radical.The peroxides or azo compounds used for polymerization processes can beused as radical formers. The polymerization is performed preferably insolution, and is of the nature of a precipitation polymerization sincepolypentabromobenzylacrylate and polypentabromobenzylmethacrylate areinsoluble in ordinary organic solvents up to temperatures around 150° C.The polymerization is performed generally from 0° to 150° C., preferably20° to 140° C.

Thermoplastic un-crosslinked copolymers are also obtained whenunsaturated esters of Structural Formula 1, wherein n = 1, such as forexample pentabromobenzylacrylate or pentabromobenzylmethacrylate, arecopolymerized with comonomers having a polymerization-active C═C doublebond, such as styrene or methylmethacrylate or other monomers.

If styrene or methylmethacrylate are copolymerized conventionally withcommercial acrylic esters, an internal plasticizing effect is produced:the glass temperature of the copolymers, their rigidity and theirthermal stability of shape diminish as the content of the acrylic esterbasic building blocks in the copolymer increases.

In contrast, the copolymerization of styrene or methyl methacrylate withthe unsaturated esters of Formula 1 in which n = 1 results even in anincrease in the thermal stability of shape and in the chemical stabilityof the copolymers, while the glass temperature and mechanical propertiesremain the same. The Vicat thermal stability of shape of a copolymer ofstyrene with approximately 6 mole-% of pentabromobenzyl acrylate basicbuilding blocks is 8° to 10° C. higher, and that of a copolymer ofstyrene with approximately 6 mole-% of pentabromobenzylmethacrylate is12° to 15° C. higher, than that of a homopolystyrene. The same appliesto copolymers with methylmethacrylate.

Another advantage of the copolymers consists in their fire resistance orincombustibility.

The advantage of the flame-proofing method of the invention is that theflame-proofing agent is combined with the thermoplastics bycopolymerization (and hence homeopolar bonding), which makeschalking-out impossible.

Furthermore, since the flame-proofing agent is in no way a filler, noimpairment of the mechanical properties occurs. In fact, improvements,especially of thermomechanical characteristics, are achieved.

The copolymerization of the unsaturated esters of Structural Formula 1wherein n is equal to 1 with styrene or acrylic or methacrylic estersand/or other comonomers takes place in accordance with a radicalmechanism. Organic or inorganic peroxides or aliphatic azo compounds areused as radical formers. Dibenzoyl peroxide, dicumyl peroxide orpotassium peroxydisulfate, and azodiisobutyric acid nitrile are usedwith preference. The radical formers can be excited to decomposition byhigh-energy radiation or by a redox reaction.

Conventional polymerization temperatures are used, generally rangingfrom 0° to 150° C.

The copolymerization can be performed in substance, in solutions or insuspension. Surprisingly it has been found that, although thebromine-containing unsaturated esters of Structure 1 are crystallizedcompounds of high melting points (pentabromobenzylacrylate meltingpoint: 106-108° C.; pentabromobenzylmethacrylate melting point:147°-149° C.), copolymerization with styrene or with methyl methacrylatein emulsion can be performed. In this case the copolymerization behaviorof the monomeric pairs is substantially the same as in polymerization insubstance. By emulsion copolymerization, copolymers of molecular weightsas high as several tens of millions can be produced.

Crosslinked, infusible polymeric products are obtained by polymerizationor copolymerization of bromine-containing bisacrylic or bismethacrylicesters of Formula 1 with n equal to 0. The polymerization conditions asregards the radical catalysts, the temperature, etc., are the same asthose already described, and in the case of copolymerizations involvingcontents of the Formula 1 substances of up to about 20% by weight, theywill be the same as those of the polymerization of the comonomerinvolved.

If tetrabromoxylylene bisacrylates or bismethacrylates crosslinked byexhaustive polymerization are to be produced, it is not necessary to useseparate apparatus for the synthesis of the Formula 1 monomers of n = 0from acrylic or methacrylic acid and tetrabromoxylylene dichloride andfor the crosslinking radical polymerization that follows. Both thecondensation reaction for the formation of the ester and thepolymerization can be performed in a "one-pot reaction" withoutisolation or refinement of the intermediate product of Formula 1. Thecrosslinked polymer, which precipitates in insoluble form, is suctionfiltered, washed with organic solvents, washed free of chloride withwater, and dried.

Both the uncrosslinked thermoplastic polymers or copolymers of thebromine-containing acrylic or methacrylic esters of Formula 1 wherein n= 1, and the crosslinked polymers or copolymers of thebromine-containing bisacrylic or bismethacrylic esters of Formula 1wherein n = 0, have a thermal stability that is unusual for bromatedorganic compounds and permits the polymers and copolymers of theinvention to be fabricated without problems and to be employed attemperatures as high as 200°-300° C. without danger of decomposition orthermal damage.

The bisacrylates and bismethacrylates of Structure 1 with n = 0 are alsointeresting components for thermosetting resins (for radicalcrosslinking).

In this connection one can, after shaping the bisesters, harden them insubstance, or also combine them with other acrylates or bisacrylates asa reactive crosslinking component.

Particularly interesting are casting resins consisting oftetrachloroxylylene bisacrylate or bismethacrylate, styrene, andtetrabromoxylylene bisacrylate or bismethacrylate as flame-inhibitingcomponents. These are casting resins which, in the cured state, areequal in their mechanical and thermomechanical properties to theunsaturated polyester resins of high stability of shape. Thecrosslinking copolymerization of the bromated unsaturated esters ofFormula 1 with n = 0 with the other resin components results in anoptimum distribution of the flameproofing agent which is anchored intothe casting resin by homeopolar binding, which assures optimumflameproofing action and prevents the flameproofing agent from chalkingout.

Solutions of unsaturated polyester resins in styrene are alsooutstandingly suitable as "comonomers" for tetrabromoxylylene diestersof Formula 1 with n = 0.

Unsaturated polyester resins on the basis of unsaturated and, in somecases, saturated dicarboxylic acids, such as maleic acid and maleic acidanhydride, fumaric acid, phthalic acid anhydride, isophthalic andterephthalic acid, and on the basis of alcohols such as ethylene glycoland neopentyl glycol, can be dissolved in a reactive monomer such asstyrene to form casting resins. In the hardening process, the maleinateor fumarated double bonds of the unsaturated polyester resin react withthe double bonds of the styrene with a radical crosslinkingpolymerization. If the tetrabromoxylylene diesters of Formula 1 with n =0 are added as a third component to the solutions of unsaturatedpolyester resins in styrene, they participate in the crosslinkingprocess, resulting in valuable improvements in the properties of thecastings. For example, the Martens thermal stability of shape of anunsaturated polyester resin on the basis of 0.5 mole of neopentylglycol, 0.5 mole of ethylene glycol, 0.4 mole of phthalic acid anhydrideand 0.6 mole of fumaric acid, dissolved 50 to 60 parts by weight in 50to 40 parts by weight of styrene and hardened, is increased by 10° to15° C. by the addition of 15 wt.-% of tetrabromoxylylene bisacrylate tothe styrene solution, and by more than 20° C. by the addition of 20wt.-%, while at the same time the impact strength and notch impacttoughness surprisingly remain unaffected. Not only the thermal stabilityof shape but also the ball impression hardness is increased by theaddition of the bisacrylate. Generally, the molecular weight of suchun-crosslinked unsaturated polyester is 500 to 7000.

Crosslinking copolymerization with 15 wt.-% and 20 wt.-% oftetrabromoxylylene bisacrylate introduces 8.5 and 11.3% of bromine,respectively, into the hardened unsaturated polyester resin, so that, bythe addition of 5% and 7% by weight, respectively, of antimony trioxide,self-extinguishing castings can be obtained with a rating of 94/VO inthe Underwriters' Laboratories test.

Additional subject matter of the invention is the use of the polymers asflameproofing agents for plastics or as flameproofed plastics. Ofespecial value are the polymers of the tetrabromoxylylene acrylates,including both those made from the invididual isomers and those madefrom mixtures thereof.

The copolymers containing less than about 40% by weight of thesubstances of Formula 1 can be fabricated directly into fire-resistantarticles, the special advantages mentioned above being achieved in likemanner.

It has been found that by flameproofing according to the presentinvention problems such as chalking-out are solved. Moreover, highquantities of flameproofing agent are not required to combat the normalmigration of polymeric composition of flameproofing agent which isexperienced. The flameproofing agents of the present invention arechemically related to the plastics to which they impartflame-retardency. They function ideally as components of the plasticcomposition and do not significantly provide an undesirable andbrittling effect.

Preferably, the flameproofing agents are to contain chlorine and/orbromine in amounts of 35 to 85%, preferably 45 to 75%, by weight. Theycan be added to the thermoplastics in amounts of 5 to 20%, preferably 7to 12%, by weight. They are preferably to have a high degree ofpolymerization and a melting point above 150° C., preferably above 200°C.

In order to more fully illustrate the nature of the invention and themanner of practicing the same the following examples are presented.

It is one aspect of the invention that homo- and copolymers of thebismethacrylates are crosslinked and their molecular weight is up to ∞.Homopolymers often are insoluble and their molecular weight is in therange of 10,000 to 5,000,000. Some copolymers have low molecular weightsbetween 500 and 5000, others have molecular weights up to 10 · 10⁶.

It is a special aspect of the invention to use tetrabromoxylenebisacrylate homopolymers themselves and in some cases copolymers asflame retardents in an amount of 5 to 15 weight percent in combustibleplastics. It is also possible to use these flame retardents in admixturewith other plastic products, e.g. polyethylene, polystyrene, especiallyarylesters such as polybutylene terephthalates containing crosslinkedbrominated polybisacrylates.

EXAMPLES EXAMPLE 1 -- Polymerization of pentabromobenzyl acrylate

200 g of pentabromobenzyl acrylate (M.P. 106°-108° C.) is dissolved inone liter of methyl glycol at 80° C. in a three-necked flask providedwith a paddle stirrer, a gas introduction tube and a reflux condenser.Under a slow stream of nitrogen, 4 g of dibenzoyl peroxide paste (50%paste) is added as polymerization initiator. After a few minutes ofinduction time, the colorless polypentabromobenzyl acrylate begins toprecipitate in powder form. After 2 h of polymerization time the flaskcontains a suspension of polymerizate. 2 g of dibenzoyl peroxide pasteis added, the temperature is raised to 90° C. for 3 hours, and then, tocomplete the polymerization, for 4 hours at 110° C. and for 1 hour at120° C.

The polymer suspension thus obtained is suction filtered hot, washedonce with methyl glycol and then with water, and dried at 120° C. toconstant weight. 186 g of polypentabromobenzyl acrylate is obtained,which corresponds to a yield of 93%.

The melting range of the polymer is 205° to 215° C. on the Koflerheating bench. The bromine content as determined by elemental analysisis 70.8%.

On the thermoscale, at a heating rate of 8° C./min in an air atmosphere,the polymer undergoes the following weight losses: 1% at 315° C.; 5% at326° C. and 10% at 332° C. The weight loss under constant exposure to200° C. in air is 2.2% over a period of 72 hours.

At room temperature as well as at 100° C., polypentabromobenzyl acrylateis insoluble in ordinary organic solvents such as aliphatic and aromatichydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers such asdioxane or tetrahydrofuran, esters and ketones, and in dimethylformamideand dimethylsulfoxide.

EXAMPLE 2 -- Preparation of polypentabromobenzyl acrylate frompentabromobenzyl chloride and acrylic acid.

75.7 g (1.05 moles) of acrylic acid and 2 g of hydroquinone aredissolved in 800 ml of methyl glycol in a three-necked flask providedwith paddle stirrer, gas introduction tube and reflux condenser, and53.26 g of anhydrous soda (0.5025 mole) is added in portions to formsalt. Then 521 g (1 mole) of pentabromobenzyl chloride is added andheated at 110° C. for 3.5 hours. Chloride determination by Mohr's methodshowed a transformation to pentabromobenzyl acrylate of 97.2%.

The mixture was diluted with one liter of methyl glycol, 10 g of dicumylperoxide was added as polymerization initiator, and the temperature wasraised to 120° C. After 15 h of polymerization, the suspension thatformed was worked up as in Example 1. 437 g of polypentabromobenzylacrylate was obtained, which corresponds to a yield of about 86% withrespect to pentabromobenzyl chloride.

EXAMPLE 3 -- Preparation of polypentabromobenzyl methacrylate frompentabromobenzyl chloride and methacrylic acid.

In a reaction vessel like the one in Example 1, 9.04 g (0.105 mole) ofmethacrylic acid and 0.2 g of hydroquinone were dissolved under a slowstream of nitrogen in 100 ml of methyl glycol, and 5.3 g (0.0502 mole)of anhydrous sodium carbonate was added in portions for the formation ofsalt. Then 52.1 g (0.1 mole) of pentabromobenzyl chloride was added andthe mixture was heated for 2 h at 110° C. Determination of chloride byMohr's method indicated a transformation to pentabromobenzylmethacrylate of 98.4%. The mixture was diluted with 100 ml of methylglycol, 1.2 g of dicumyl peroxide was added as polymerization initiator,and under a slow stream of nitrogen the temperature was raised to 125°C. After 7 h of polymerization, the product is worked up as inExample 1. 51 g of polypentabromobenzyl methacrylate is obtainedcorresponding to a yield of 89% with respect to pentabromobenzylchloride. The polymer has a bromine content, determined by elementalanalysis, of 69.2%. The melting range as determined on the Kofler benchis 210° to 225° C. The weight loss on the thermoscale in air, using aheating rate of 8° C./min amounts to 1% at 319° C.; 5% at 332° C. and10% at 337° C.

The solubility is the same as that of polypentabromobenzyl acrylate.

EXAMPLES 4-11 -- Copolymerization of pentabromobenzyl acrylate withstyrene in solution.

To determine the copolymerization behavior of the above-mentionedmonomer pair, a number of copolymerization batches were polymerized withdifferent monomer ratios in the starting mixture to a maximumtransformation of 50% by weight, and the copolymers obtained wereanalyzed. The following Table 1 shows the polymerization conditions andresults. Styrene is slightly preferred in the copolymerization withpentabromobenzyl acrylate.

                                      Table 1:                                    __________________________________________________________________________    Copolymerization of styrene (M.sub.1) and pentabromobenzyl acrylate           (M.sub.2) in solution.                                                        Initiator: Azodiisobutyric acid nitrile, 1 wt.-%                              Temperature: 60° C                                                      Ex. No.                                                                          Sty- rene (M.sub.1)  g                                                            Pentabromo- benzyl acrylate (M.sub.2)  g                                              Molar ratio.sup.1) M.sub.1 :M.sub.2                                                ##STR6##                                                                            Ben- zene  g                                                                      Time  h                                                                          Copoly- mer  g                                                                      Bro- mine con- tent %                                                             Molar ratio.sup.2) m.sub.1                                                   :m.sub.2                                                                            ##STR7##                                                                            Melting                                                                      temp..sup.3)                                                                  (Kofler bench)                                                                ° C              __________________________________________________________________________    4  9.36  5.56  90:10   0.9                                                                              15  5  5.4   --  --    0.97 150 - 160               5  4.16  5.56  80:20  0.8 9.5 4  4.3   --  --    0.84 approx. 160             6  1.56  5.56  60:40  0.6 7.5 4  3.2   --  --    0.75 approx. 165             7  1.3   6.7   50/50  0.5 8   5  3.5   --  --    0.66 approx. 170             8  1.04  8.34  40:50  0.4 9.5 5  4.0   57.3                                                                              1.35  0.57 approx. 150             9  0.78  9.73  30:70  0.3 10.5                                                                              4  7.05  65.6                                                                              0.51  0.33 95 - 105                10 0.26  5.56  20:80  0.2 6   5  3.8   64.2                                                                              0.62  0.38 80 - 90                 11 0.13  6.24  10:90  0.1 6.5 4  5.75  68.9                                                                              0.22  0.18 135                     __________________________________________________________________________                                                          - 145                    .sup.1) Molar ratio of the monomers in the initial mixture.                   .sup.2) Molar ratio of the basic building blocks in the copolymer, based      in Examples 4 to 7 on quantitative NMR spectroscopy, and in Examples 8 to     11 on the                                                                     bromine content of the copolymers as determined by elemental analysis         according to the equation:                                                    ##STR8##                                                                      .sup.3) The melting temperature of a styrene homopolymer was determined t     be 135 - 145° C.                                                  

EXAMPLE 12 -- Copolymerization of pentabromobenzyl acrylate with styrenein emulsion.

In a reaction vessel equipped with a paddle stirrer and a nitrogen feedtube, 550 g of water and 21 g of sodium stearate were heated at 50° C.101 g of pentabromobenzyl acrylate was dissolved in 300 g of styrene at50° C. (molar ratio 6:94) and stirred into the soap solution.

0.92 g of potassium peroxydisulfate was added to the emulsion as apolymerization initiator, and the mixture was stirred for 24 h undernitrogen at 50° C.

The copolymer was flocculated by pouring the latex into aqueous aluminumsulfate solution, washed with water and dried until the weight wasconstant. Yield 398 g equal to 99% by weight. Bromine content 17.6% byweight (determined by elemental analysis). Content of pentabromobenzylacrylate basic building blocks in the copolymer 6.2 ± 1.5 mole-% (NMRspectroscopy). Reduced specific viscosity η_(sp/c) = 15.6 dl/g(chloroform 25°, 1% solution). Molecular weight M_(GPC) = 2 · 10⁶ (gelchromatography in tetrahydrofuran). The weight losses measured on thethermoscale in air at a heating rate of 8° C. per minute were 1% at 308°C., 5% at 320° C. and 10% at 334° C.

On pressed plates and from strandard size test pieces sawed therefrom,the following properties were determined in comparison to ahomopolystyrene prepared by emulsion polymerization (molecular weightM_(GPC) ≈ 1.3 · 10⁶).

    ______________________________________                                                          Copolymer                                                                             Polystyrene                                         ______________________________________                                        Ball impression hardness                                                                     N/mm.sup.2                                                                             138       145                                         Ultimate tensile strength                                                                    N/mm.sup.2                                                                             46        38                                          Bending strength                                                                             N/mm.sup.2                                                                             76        84                                          Impact strength                                                                              KJ/m.sup.2                                                                             10.2      8.1                                         Notch impact toughness KJ/m.sup.2                                                            3.1      2.0                                                   Vicat temperature                                                                            ° C                                                                             111       89                                          Martens temperature                                                                          ° C                                                                             78        66                                          Combustibility, UL test 94/V0     failed test                                 ______________________________________                                    

EXAMPLES 13-15 -- Copolymerization of pentabromobenzyl acrylate withstyrene in emulsion.

In reaction vessels like those of Example 12, 550 ml of water is placed,and 21 g of sodium stearate is dissolved therein. 33.3 g ofpentabromobenzyl acrylate is dissolved in 30.57 g of styrene (molarratio of the monomers 2:98) in the case of Example 13, 50.1 g ofpentabromobenzyl acrylate in 302.4 g of styrene (molar ratio 3:97) inExample 14, and 58.5 g of pentabromobenzyl acrylate in 300.9 g ofstyrene (molar ratio 3.5:96.5) in Example 15, and the monomer mixturesare stirred into the soap solutions heated at 50° C. 1.0 g of potassiumperoxydisulfate is added as polymerization initiator and the mixture isstirred for 24 hours at 50° C. under a slow stream of nitrogen.

The copolymers of Examples 13 to 15 are precipitated by flocculation andprocessed as in Example 12. The polymerization yields, at 99% by weight,are virtually quantitative. The bromine content as determined byelemental analysis amounts to 7.1, 9.7 and 11.2 percent, respectively,in the copolymers of Examples 13, 14 and 15. On this basis the contentof pentabromobenzyl acrylate basic building blocks in the copolymer ofExample 13 is reckoned at 2 mole-%; in the copolymers of Examples 14 and15 it is reckoned at 2.8 and 3.4 mole-%, respectively. This is in goodagreement with the values determined by nuclear magnetic resonancespectroscopy: 1.8, 3.2 and 3.8 mole-%. The reduced specific viscositiesdetermined in 1% chloroform solution amount to 20.0, 34.2 and 33.0 dl/g,respectively.

The copolymers are mixed with 5 wt.-% of Sb₂ O₃, made into a rollerskin, and pressed to form sheets 1 mm and 4 mm thick. The combustibilityand a number of mechanical characteristics were determined.

    ______________________________________                                                       2 mole-%                                                                      of                                                                            penta-                                                         Copolymer      bromo-    2.8 mole-%                                                                              3.4 mole-%                                 containing     benzyl    acrylate  basic units                                ______________________________________                                        Bending strength N/mm.sup.2                                                                  82        96        68                                         Impact strength KJ/m.sup.2                                                                   8.6       9.2       10.0                                       Notch impact strength                                                         KJ/m.sup.2     2.2       2.8       2.4                                        Vicat temperature ° C                                                                 106       104       105                                        Martens temperature ° C                                                               78        77        82                                         Combustibility in UL test                                                                    94/V2     94/V2     94/V0                                      ______________________________________                                    

EXAMPLE 16 -- Copolymerization of pentabromobenzyl methacrylate withstyrene in emulsion.

360 ml of water was placed in a reaction vessel equipped with a paddlestirrer and a gas introduction tube, 14 g of sodium stearate was added,and the soap solution was heated at 60° C. 68.4 g of pentabromobenzylmethacrylate was dissolved in 195.2 g of styrene at 60° C. (molar ratio6 : 94) and the monomer mixture was stirred into the soap solution. 0.6g of potassium peroxydisulfate was added as polymerization initiator,and the mixture was stirred for 24 hours under a slow stream ofnitrogen. After the latex had been flocculated, washed and driec, 257 gof a copolymer was obtained having a bromine content of 16.8% and areduced specific viscosity as determined in 1% of chloroform of 28 dl/g.

When pressed to form a 4 mm thick board, the copolymer has a bendingstrength of 89 N/mm², an impact strength of 11 KJ/m², a Vicattemperature of 117° C. and a Martens temperature of 86° C.

Without flame-retardant additives the copolymer has a rating of 94/V1 inthe UL test.

EXAMPLES 17-25 -- Copolymers of pentabromobenzyl acrylate with methylmethacrylate in solution.

To determine the copolymerization performance of pentabromobenzylacrylate with methyl methacrylate, a number of batches containingvarious ratios of monomers in the starting mixture were polymerized to amaximum transformation of 50% by weight, and the copolymers thusobtained were analyzed. Table 2 shows the polymerization conditions andthe results. Methyl methacrylate is incorporated in the copolymerizationwith pentabromobenzyl acrylate with only a slight degree of preference.

                                      Table 2:                                    __________________________________________________________________________    Copolymerization of Methyl Methacrylate (M1) with Pentabromobenzyl            Acrylate (M2) in solution.                                                    Initiator: Azodiisobutyric acid nitrile, 1% by weight                         Temperature: 60° C; 50% solution in benzene                             Ex. No.                                                                          M1 (g)                                                                           M2 (g)                                                                           M1:M2*                                                                             ##STR9##                                                                             Time (min)                                                                        Copolymer (g)                                                                        Transformation (wt.-%)                                                                 Bromine content (%)                                                                 m1:m2**                                                                            ##STR10##                __________________________________________________________________________    17 9.0                                                                               5.56                                                                            90:10                                                                              0.9    75  4.55   31.4     --    --   0.95                      18 8.0                                                                              11.12                                                                            80:20                                                                              0.8    75  7.55   39.5     --    --   0.89                      19 3.5                                                                               8.34                                                                            70:30                                                                              0.7    75  4.2    35.4     --    --   0.79                      20 3.0                                                                              11.17                                                                            60:40                                                                              0.6    75  6.6    46.5     --    --   0.71                      21 1.25                                                                              6.7                                                                             50:50                                                                              0.5    60  2.4    30.0     --    --   0.62                      22 1.0                                                                               8.34                                                                            40:60                                                                              0.4    60  4.7    50.2     59.9  1.11 0.52                      23 1.5                                                                              19.46                                                                            30:70                                                                              0.3    40  8.7    41.2     67.9  0.33 0.24                      24 0.5                                                                              11.12                                                                            20:80                                                                              0.2    40  5.0    43.3     67.6  0.35 0.25                      25 0.25                                                                             12.48                                                                            10:90                                                                              0.1    30  5.3    41.5     70.3  0.12 0.10                      __________________________________________________________________________     *Molar ratio of the monomers in the starting mixture.                         **Molar ratio of the basic building blocks in the copolymer; in Examples      17 to 20 this was determined by quantitative NMR spectroscopy, and in the     other examples                                                                it was based on the bromine content of the copolymers as determined by        elemental analysis, in accordance with the equation:                          ##STR11##                                                                

EXAMPLE 26 -- Copolymerization of pentabromobenzyl acrylate with methylmethacrylate in emulsion.

In a reaction vessel equipped with a paddle stirrer and a gasintroduction tube, 19 g of sodium stearate is dissolved in 500 ml ofwater. 50.1 g of pentabromobenzyl acrylate is dissolved at 50° C. in 291g of methyl methacrylate and the monomer mixture is stirred into theaqueous soap solution heated at 50° C. After the addition of 1.2 g ofpotassium peroxydisulfate, the mixture is polymerized for 24 hours at50° C. under a stream of nitrogen.

The polymer is separated as before, and washed with water and methanol,and dried. Yield 331 g (bromine content 8.7 wt.-%). A pressed 4 mm thickboard had a bending strength of 90 N/mm², and an impact strength of 9KJ/m², a notch impact toughness of 1.8 KJ/m², a Vicat temperature of117° C. and a Martens temperature of 96° C.

For comparison, a homopolymer of methyl methacrylate prepared inemulsion analogously to Example 26 has the following characteristics:bending strength 102 N/mm², impact strength 7.5 KJ/m², notch impactstrength 1.4 KJ/m², Vicat temperature 98° C., and Martens temperature89° C.

EXAMPLE 27 -- Copolymerization of pentabromobenzyl acrylate with methylmethacrylate in emulsion.

By the procedure of Example 26, a monomer mixture consisting of 66.6 gof pentabromobenzyl acrylate and 288 g of methyl methacrylate issubjected to copolymerization. 343 g of a copolymer is obtained having abromine content of 13.1%.

EXAMPLE 28 -- Copolymerization of pentabromobenzyl acrylate with methylmethacrylate in substance.

9.4 g of methyl methacrylate and 3.34 g of pentabromobenzyl acrylateplus 0.13 g of azodiisobutyric acid nitrile are weighed into apolymerization vessel and the mixture is polymerized in a nitrogenatmosphere for 15 h at 50° C.

After dissolution in chloroform and precipitation in methanol, followedby washing and drying, 11.4 g of a copolymer is obtained having abromine content of 15.8%, a content of 5.3 mole-% of pentabromobenzylacrylate building blocks as determined by quantitative NMR spectroscopy,and a reduced specific viscosity of 1.75 dl/g determined in chloroform(1% solution). The molecular weight determined in THF is: M_(GPC) =210,000, and the softening temperature on the Kofler bench is 180° to200° C. The weight losses on the thermal scale (air atmosphere, heatingrate 8° C./min) are 1% at 273° C., 5% at 286° C. and 10% at 294° C.

The Vicat temperature of a pressed specimen is 119° C.

EXAMPLE 29 -- Crosslinking polymerization of tetrabromoxylylenebisacrylate.

In a reaction vessel as above, 210 g of tetrabromo-p-xylylenebisacrylate (M.P. = 151°-154°) is dissolved in 760 ml of methyl glycolat 80° C., 8 g of dibenzoyl peroxide paste (50% paste) is added aspolymerization initiator, and the mixture is polymerized for 4 h at 80°C., 3 h at 90° C. and 2 h at 110° C. under a nitrogen stream. Uponcessation of the reaction a suspension of polymer has formed. Thesuspension is suction filtered, washed with methanol and then withwater, and dried. 198 g is obtained of a crosslinked, insoluble andinfusible powdered polymer having a bromine content of 56.6% and thefollowing grain size distribution: larger than 500 μ 3.4 wt.-%; 200-500μ 23.68 wt.-%; 150-200 μ 15.04 wt.-%; 100-150 μ 42.8 wt.-%; 71-100 μ13.04 wt.-%; smaller than 71 μ 1.48 wt.-%. On the thermal scale, in air,at a heating rate of 8° C./min., the crosslinked bisacrylate showed thefollowing weight losses: 1% at 296° C.; 5% at 324° C. and 10% at 332° C.

EXAMPLE 30 -- Crosslinking polymerization of tetrabromo-p-xylylenebismethacrylate.

By the same procedure as in Example 29, 200 g of tetrabromo-p-xylylenebismethacrylate (M.P. 148°-149° C.) yielded, upon crosslinkingpolymerization, 192 g of an insoluble and infusible polymer having abromine content of 54.1%.

EXAMPLE 31 -- Preparation of crosslinked tetrabromoxylylene bisacrylatefrom tetrabromoxylylene dichloride and acrylic acid.

In a three-necked flask as above, 38 g (0.53 mole) of acrylic acid and0.075 g of hydroquinone are dissolved in 300 ml of methyl glycol and28.25 g of anhydrous soda is added in portions, with stirring, over aperiod of 1 h. 123 g (0.25 mole) of tetrabromoxylylene dichloride isomermixture consisting of 50% m- and 25% each o- and p-isomer is added, andthe temperature is raised to 120° C. After 2.5 h at 120° C., 150 ml ofmethyl glycol and 2.5 g of dicumyl peroxide as polymerization initiatoris added, and the mixture is polymerized in a stream of nitrogen for 2 hat 120° C. and 3 h at 130° C. The crosslinked tetrabromoxylylenebisacrylate is separated by suction filtration, washed once with methylglycol, and then washed chloridefree with water.

After drying at 120° C., 139 g of an infusible, crosslinked, powderedpolymer is obtained having a bromine content of 56.7% and a sodiumcontent of less than 0.001%.

Screen analysis:

    ______________________________________                                        >750 μ             3.04 wt.-%                                              250 - 750 μ       29.28 wt.-%                                              150 - 200 μ       19.76 wt.-%                                               71 - 100 μ       19.04 wt.-%                                              >71 μ             28.24 wt.-%                                              ______________________________________                                    

Weight loss (thermal scale, in air, heating rate 8° C. per minute): 1%at 287° C., 5% at 319° C. and 10% at 337° C. The weight loss in airunder constant exposure to 200° C. is 2.26% at the end of 3 hours and3.82% at the end of 48 hours.

EXAMPLE 32 -- Tetrabromoxylylene bisacrylate as a reaction component ina bisacrylate resin composition.

A mixture of 100 g of p-xylylene bisacrylate (M.P. 72°-75° C.), 50 g oftetrachloro-m-xylylene bismethacrylate (M.P. 83° C.) and 25 g oftetrabromo-p-xylylene bisacrylate was melted; 1 wt.-% of dicumylperoxide was added as setting catalyst, and the mixture was poured intomolds. The thermosetting is performed for 3 h at 115° C. and curing at135° C. for 4 h. Transparent, virtually colorless boards of 4 mm and 2mm thickness, respectively, were prepared, which had a chlorine contentof 9.7% and a bromine content of 8%.

The 4 mm board had an impact strength of 4.8 KJ/m² and a thermalstability of shape of 99° C. (Martens) and 111° C. (ISO/ R 75; A). Inthe UL test, the 2 mm board was self-extinguishing; rating: 94 / VO.

For comparison, a 4 mm thick board made by the same procedure from acasting resin mixture consisting of 125 g of p-xylylene bisacrylate and50 g of tetrachloro-m-xylylene bismethacrylate had an impact strength of5.2 KJ/m² and a thermal stability of shape of 87° C. Martens and 96° C.ISO/R 75; A. A casting 2 mm thick did not pass the UL test 94.

EXAMPLE 33 -- Tetrabromoxylylene bisacrylate as reaction component in abisacrylate resin composition.

A resin mixture consisting of 150 g of tetrachloro-m-xylylenebisacrylate (M.P. 65°-67° C.) and 25 g of tetrabromo-p-xylylenebisacrylate is melted; 1 wt.-% of dibenzoyl peroxide 50% paste is added,and the mixture is hardened in a mold for 3 h at 85° C. and then curedfor 4 h at 130° C. to form a board 4 mm thick having the followingcharacteristics:

    ______________________________________                                        Bending strength:      110 N/mm.sup.2                                         Ball impression hardness, 30 sec.                                                                    126 N/mm.sup.2                                         Impact strength        4.6 KJ/m.sup.2                                         Notch impact strength  1.6 KJ/m.sup.2                                         Thermal stability of shape, Martens                                                                  104° C                                          Thermal stability of shape, ISO/R75; A                                                               119° C                                          ______________________________________                                    

EXAMPLE 34 -- Tetrabromoxylylene bisacrylate as reactant in a styrenesolution of bisacrylate resin.

300 g of tetrachloro-p-xylylene bisacrylate (M.P. 116°-117° C.) and 100g of tetrabromo-p-xylylene bisacrylate (M.P. 151°-154° C. are dissolvedin 400 g of styrene. After the addition of 2 wt.-% dibenzoyl peroxide50% paste, the resin solution is cast in molds and set for 4 h at80°-85° C. and then cured for 4 h at 135° C. A 4 mm thick board has abending strength of 123 N/mm², a ball impression hardness (30 sec) of134 N/mm², an impact strength of 6.7 KJ/m² and a thermal stability ofshape of 126° C. Martens and 138° C. ISO/R 75; A). In the UL test a 2 mmthick board is self extinguishing and has a rating of 94/VO.

EXAMPLES 35-37 -- Tetrabromoxylylene bisacrylate as cross-linkingcomponent in unsaturated polyester resin solutions.

An unsaturated polyester resin was prepared on the basis of 0.5 mole ofethylene glycol, 0.5 mole of neopentyl glycol, 0.4 mole of phthalic acidanhydride, and 0.6 mole of fumaric acid. The resin, with a gelchromatographic molecular weight M_(GPC) of 2800, is dissolved 50wt.-parts in 50 wt.-parts of styrene, and tetrabromo-p-xylylenebisacrylate is added to this styrene solution of unsaturated polyesterresin in amounts of 15 and 20 wt.-% of the total amount (Examples 36 and37, respectively). After setting (cold setting with 2% of a 50% paste ofdibenzoyl peroxide and 0.2 mole-% of a 10% solution of dimethyl aniline)at 50° C. and curing at 135° C. for 4 h, transparent boards 4 mm thickwere obtained having the following characteristics. For comparison, thevalues are also given for the cured styrene solution of the unsaturatedpolyester resin solution without the addition of bisacrylate (Example35).

    ______________________________________                                                        UP resin            Bisac-                                                    solution  UP resin  rylate                                                    without   solution  wt.-%                                                     addition  85 : 15   80 : 20                                   Example No.     35        36        37                                        ______________________________________                                        Ball impression hardness,                                                     30 sec., N/mm.sup.2                                                                           1480      1530      1690                                      Impact strength, KJ/m.sup.2                                                                   5.8       6.2       5.9                                       Thermal stability of shape:                                                   Martens ° C                                                                            95        112       117                                       ISO/R 75; A ° C                                                                        114       127       139                                       ______________________________________                                    

By the addition of 15 wt.-% of the tetrabromoxylylene bisacrylate, thethermal stability of shape of the cured UP resin is increased by about15° C., and by the addition of 20 wt.-% it is increased by about 20° C.,without loss of impact strength. An improvement in the ball impressionhardness is also to be observed.

If 5% and 7% by weight of antimony trioxide is added, with stirring, tothe UP resin solutions treated with tetrabromoxylylene bisacrylate inExamples 36 and 37, respectively, before they are hardened,self-extinguishing castings are obtained in the UL test; rating: 94/VO.

EXAMPLE 38 -- Crosslinking polymerization of tetrabromo-m-xylylenebisacrylate.

In a reaction vessel equipped with a paddle stirrer, gas introductiontube and a reflux condenser, 200 g of tetrabromo-m-xylylene diacrylatewith a melting point of 105°-108° C. is dissolved in 800 ml of methylglycol with heating. Under a slow stream of nitrogen, 2 grams of dicumylperoxide, corresponding to 1% of the weight of the monomer, are added aspolymerization initiator, and the mixture is heated to thepolymerization temperature of 125° C. The mixture begins to becometurbid as a result of precipitating crosslinked polymer, and by the timeone hour has elapsed a doughy polymer suspension has formed.Polymerization proceeds for a total of 6 hours at 125° C., and then thepolymer is suction filtered, washed with methanol and then with water,and dried up to 150° C.

189 g is obtained of a crosslinked, insoluble and infusible, powdered,colorless polymer having a bromine content of 54.8% and a chloridecontent of 0.9%. Acrylic ester double bonds are no longer detectable byinfrared analysis.

On the thermoscale in air at a heating rate of 8° C. per minute, thecrosslinked product shows the following weight losses: 1% at 302° C., 5%at 318° C., 10% at 326° C.

The screen analysis of the crosslinked bisacrylate is:

    ______________________________________                                        >500 μ             2.8 wt.-%                                               200 - 500 μ        6.9 wt.-%                                               150 - 200 μ       16.0 wt.-%                                               100 - 150 μ       48.2 wt.-%                                                70 - 100 μ       21.5 wt.-%                                               <70 μ              4.6 wt.-%                                               ______________________________________                                    

EXAMPLE 39 -- Crosslinking polymerization of tetrabromo-m-xylylenebismethacrylate.

By the same procedure as in Example 38, 200 g of tetrabromo-m-xylylenebismethacrylate with a melting point of 97°-99° C. is crosslinkinglypolymerized in 600 ml of methyl glycol with the use of 1.4 g of dicumylperoxide. 193 g of an insoluble, infusible polymer powder is obtainedhaving a bromine content of 53.8%. The weight loss on exposure to air at200° C. is 2.4% in 24 h and 2.9% in 48 h.

EXAMPLE 40 -- Crosslinking polymerization of tetrabromo-o-xylylenebisacrylate.

In a reaction vessel equipped with a paddle stirrer, reflux condenserand gas introduction tube, 100 g of tetrabromo-o-xylylene bisacrylatewith a melting point of 100° to 102° C. is dissolved with heating in 400ml of methyl glycol and, under a slow stream of nitrogen, 3 g ofdibenzoyl peroxide 50% paste, corresponding to 1.5 wt.-% of dibenzoylperoxide, is added as initiator, and the mixture is adjusted to thepolymerization temperature of 80° C. It is then polymerized for 3 h at80° C., 3 h at 90° C. and 2 h at 110° C. The polymer suspension thatforms is suction filtered off, washed with methanol, and dried at 150°C. until its weight becomes constant.

96 g of a crosslinked, insoluble and infusible, colorless, powderedpolymer is obtained having a bromine content of 56.1%.

Acrylic ester double bonds are no longer detectable by infraredanalysis.

The weight loss during exposure to air at 200° C. is 2.9% in 24 h and3.2% in 48 h.

EXAMPLE 41 -- Preparation of crosslinked tetrabromo-m-xylylenebisacrylate from tetrabromo-m-xylylene dichloride and acrylic acid.

To a solution of 156.6 g (2.3 moles) of acrylic acid and 0.3 g ofhydroquinone in 1.8 liters of methyl glycol, 84 g (2.1 moles) of sodiumhydroxide dissolved in 84 ml of water is added. 492 g (1 mole) oftetrabromo-m-xylylene dichloride is added and the mixture is heated tothe reaction temperature of 110° C. After 1.5 hours of reaction, 8 g ofdicumyl peroxide is added and the mixture is polymerized under a slowstream of nitrogen for 6 hours at 125° C. After the product was isolatedand washed, first with methyl glycol and then with water, and dried, 537g of crosslinked, insoluble and infusible polymer was obtained. Theyield was about 96% of the theory with respect to the tetrabromoxylylenedichloride put in.

The bromine content amounted to 53.0%, the chlorine content 1.6%. Thechlorine content results from a slight bromine-chlorine exchange in thenucleus during the preparation of the tetrabromo-m-xylylene dichloridefrom the tetrabromoxylene. The weight loss on the thermal scale in airat a heating rate of 8° C./min amounts to 1% at 304° C., 5% at 312° C.and 10% at 322° C.

EXAMPLE 42 -- Preparation of crosslinked tetrabromo-o-xylylenebisacrylate from tetrabromo-o-xylylene dichloride and acrylic acid.

By the procedure of Example 41, but with the use of anhydrous soda asthe salt former, 195 g of crosslinked polymer was obtained from 61.8 gof acrylic acid, 0.11 g of hydroquinone, 45.7 g of Na₂ CO₃, 184.5 g oftetrabromo-o-xylylene dichloride and 3.75 g of dicumyl peroxide, in 675ml of methyl glycol; this corresponds to a yield of approximately 93%with respect to the tetrabromoxylylene dichloride.

The weight loss on the thermal scale in air, at a heating rate of 8°C./min, is 1% at 297° C., 5% at 320° C. and 10% at 338° C. Acrylic esterdouble bonds are no longer detectable in the infrared spectrum.

EXAMPLE 43 -- Tetrabromo-m-xylylene bisacrylate as reactant in abisacrylate resin composition.

A mixture of 100 g of p-xylylene bisacrylate (M.P. 72°-75° C.), 50 g oftetrachloro-m-xylylene bismethacrylate (M.P. 83° C.) and 25 g oftetrabromo-m-xylylene bisacrylate (M.P. 105°-108° C.) is melted, treatedwith 1 wt.-% of dicumyl peroxide as hardening catalyst, and cast inmolds. The hardening is performed for 3 h at 115° C. and the curing isperformed for 4 h at 135° C. Transparent, virtually colorless boards 4mm and 2 mm thick are prepared with a chlorine content of 9.7% and abromine content of 8%. The 4 mm board has an impact strength of 5.7KJ/m² and a thermal stability of shape of 92° C. (Martens) and 107° C.(ISO/R 75; A). The 2 mm board is self-extinguishing in the UL test;rating: 94/VO.

For comparison, a 4 mm board prepared by the same procedure from acasting resin mixture consisting of 125 g of p-xylylene bisacrylate and50 g of tetrachloro-m-xylylene bismethacrylate has an impact strength of5.2 KG/m² and a thermal stability of shape of 87° C. (Martens) and 96°C. (ISO/R 75; A). A casting 2 mm thick failed to pass UL test 94.

EXAMPLE 44 -- Tetrabromo-m-xylylene bisacrylate as reactant in abisacrylate resin composition.

A resin mixture consisting of 150 g of tetrachloro-m-xylylenebisacrylate (M.P. 65°-67° C.) and 25 g of tetrabromo-m-xylylenebisacrylate (M.P. 105°-107° C.) is melted down, tested with 1 wt.-% of a50% dibenzoyl peroxide paste and cast in a mold and hardened for 3 h at85° C. and then cured at 130° C. for 4 hours to form a 4 mm thick boardhaving the following characteristics:

    ______________________________________                                        Bending strength        123 N/mm.sup.2                                        Ball impression hardness, 30 sec                                                                      118 N/mm.sup.2                                        Impact strength         6.7 KJ/m.sup.2                                        Notch impact strength   1.9 KJ/m.sup.2                                        Thermal stability of shape:                                                   Martens                 102° C                                         ISO/R 75; A             111° C                                         ______________________________________                                    

EXAMPLE 45 -- Tetrabromo-o-xylylene bisacrylate as a reactant in astyrene solution of bisacrylate.

300 g of tetrachloro-p-xylylene bisacrylate (M.P. 116°-117° C.) and 100g of tetrabromo-o-xylylene bisacrylate (M.P. 100°-102° C.) are dissolvedin 400 g of styrene. After the addition of 2 wt.-% of a 50% paste ofdibenzoyl peroxide, the resin solution is poured into molds and set,first at 80°-85° C. for 4 h, and then at 135° C. for 4 h. A board 4 mmthick has a bending strength of 112 N/mm², an impact strength of 9.3KJ/m² and a thermal stability of shape of 115° C. (Martens) and 129° C.(ISO/R 75; A). A 2 mm thick board is self-extinguishing in the UL testand has a rating of 94/VO.

EXAMPLES 46-48 -- Tetrabromo-m-xylylene bisacrylate as a crosslinkingcomponent in unsaturated polyester resin solutions.

An unsaturated polyester resin was prepared on the basis of 0.5 mole ofethylene glycol, 0.5 mole of neopentyl glycol, 0.4 mole of phthalic acidanhydride and 0.6 mole of fumaric acid. This resin, with a molecularweight M_(GPC) = 2800 as determined by gel chromatography, is dissolved50 weight-parts in 50 weight-parts of styrene and tetrabromo-m-xylylenebisacrylate is added to this solution of UP resin in styrene in amountsof 15 and 20% of the weight of the entire mixture (Examples 47 and 48,respectively).

After hardening at room temperature with 2% of a 50% paste of dibenzoylperoxide and at 50° C. with 0.2 mole-% of a 10% solution ofdimethylaniline in styrene, and curing at 135° C. for 4 h, transparent4-mm boards were obtained having the following characteristics. Forcomparison, the characteristics of the hardened styrene solution of theunsaturated polyester resin without the addition of bisacrylate (Example46) are also given herewith:

    ______________________________________                                                        UP resin                                                                      solution                                                                      without  Ratio of UP resin solu-                                              bisac-   tion to bisacrylate:                                                 rylate   85 : 15   80 : 20                                    Example No.     46       47        48                                         ______________________________________                                        Bending strength N/mm.sup.2                                                                   93.5     107.0     116.5                                      Ball impression                                                               hardness, 30 sec N/mm.sup.2                                                                   1480     1475      1510                                       Impact strength KJ/m.sup.2                                                                    5.8      7.2       6.4                                        Thermal stability of shape:                                                   Martens ° C                                                                            95       106       112                                        ISO/R 75; A     114      124       127                                        ______________________________________                                    

The addition of 15 wt.-% of tetrabromoxylylene bisacrylate increases thethermal stability of shape of the cured UP resin by about 10° C., andthe addition of 20 wt.-% increases it by about 15° C., withoutdiminishing the impact strength. An improvement in the bending strengthis also to be observed.

If 5% and 7% of antimony trioxide, by weight, is added to the UP resinsolutions containing tetrabrom-m-xylylene bisacrylate of Examples 47 and48, respectively, before they are hardened, castings are obtained whichare self-extinguishing in the UL test; rating: 94/VO.

EXAMPLE 49

10 wt.-% of the following infusible polymers cross-linked by curing:

(a) Poly-1,2,4,5-tetrabromo-p-xylylene-1,4-bisacrylate

(b) Polytetrabromo-m-xylylene-1,3-bisacrylate

(c) Polytetrabromo-o-xylylene-1,2-bisacrylate of a polymer prepared bypolymerization of a

(d) Mixture of 40-60 wt.-% of the p-compound (a) and approximately equalparts of the m-compound (b) and the o-compound (c)

is mixed together with 5% of Sb₂ O₃ and 30 wt.-% of glass staple fibers6 mm long, plus enough polybutylene terephthalate to make 100 parts byweight, and the mixture is fabricated in an extruding machine to strandswhich are chopped into granules. The fabrication presents no difficulty;no formation of vapors and no brown discoloration is observed at thenecessary machine temperatures of 250° to 260° C. From the granules thusobtained, test specimens measuring 5 × 1/2 × 1/16 inches are injectionmolded for Underwriters Laboratories test UL 94, and tested for fireresistance. The results were ratings of "VO" for the test specimens bothas delivered and after 7 days of standing at 70° C. Samples of the testspecimens were stored for 14 days at 70° C., and others for 7 days at150° C.; in no case was any coating to be found on the surface.

If these results are compared with those obtained from a mixtureprepared precisely as described except for the use of 10 wt.-% of thecommercial flameproofing agent decabromodiphenyl or octabromodiphenylether in place of 10 wt.-% ofpoly-1,2,4,5-tetrabromo-p-xylylene-1,4-bisacrylate, the sameflameproofing is achieved, but after only 7 days at 70° C. perceptiblechalking occurs, and after 7 days at 150° C. an intense chalking isobserved.

EXAMPLE 50

Following the procedure of Example 49, but with the use of 10 wt.-% ofinfusible poly-1,2,4,5-tetrabromo-p-xylylene-1,4-bismethacrylate insteadof poly-1,2,4,5-tetrabromo-p-xylylene-1,4-bisacrylate (compound a),fire-retardant polyesters are prepared:

(A) with enough polybutyleneterephthalate to make 100 parts,

(B) with enough polyethyleneterephthalate to make 100 parts, which givegood results in the inflammability tests and have very little tendencyto chalk.

EXAMPLE 51

30% of glass fibers (6 mm) and 58% of polybutyleneterephthalate aremixed with 8% of polypentabromobenzyl acrylate (compound b, Example 49,melting range 205°-215° C.) and made into chopped granules on anextruding machine as in Example 49. The granules are injection molded toform specimens for UL test 94 and for measurement of mechanicalcharacteristics. The fabrication is performed without difficulty. ULtest 94 shows a rating of VO/VO; no chalking is observed even after 7days of exposure to heat at 150° C.

For comparison, a material is prepared after the same formula, butinstead of 8% of compound b, Example 49, the same amount of commercialpentabromodiphenyl ether is used as a flameproofing agent, which isrecommended for use in polyesters. This flameproofing agent vaporizesseverely during fabrication in the extruding machine and injectionmolding machine. UL test 94 gives a rating of only V1/V1 for thismaterial containing pentabromodiphenyl ether. No chalking occurs upon 7days of exposure to heat; if, however, the specimen in accordance withthe invention and a specimen of the material used for comparison areheated in separate glass flasks at 1 Torr for 7 hours at 150° C., thespecimen of the invention shows a weight loss of only 0.2%, while thatof the other material is 2.1%.

The mechanical characteristics were as follows:

    ______________________________________                                                             Invention                                                                            Control                                                                Specimen                                                                             Specimen                                          ______________________________________                                        Ball impression hardness                                                       DIN 53456/1/1973  N/mm.sup.2                                                                            185.0    222                                       Tensile strength, length-                                                      wise, DIN 53455   N/mm.sup.2                                                                            118.3    111.8                                     Elasticity modulus, tensile                                                    test, DIN 53457   N/mm.sup.2                                                                            98.30    91.50                                     Bending strength DIN 53452                                                                       N/mm.sup.2                                                                            162.8    161.5                                     Impact strength at +23° C                                               DIN 53453         KJ/m.sup.2                                                                            39.0     27.1                                      Notch impact stength at +23° C                                          DIN 53453         KJ/m.sup.2                                                                            11.0     8.7                                       Stability of shape on ex-                                                     posure to heat, ISO/R 75                                                       DIN 53461         ° C                                                                            190      184                                       ______________________________________                                    

The improvement in the fire resistance of the invention specimen is alsoaccompanied by a considerable improvement in important mechanicalcharacteristics.

EXAMPLE 52

8% of the flameproofing agent c used in accordance with the invention, acopolymer of 90 mole-% of pentabromobenzyl acrylate and 10 mole-% ofbutanediol monoacrylate still containing 0.2% free OH groups, arefabricated with 4% Sb₂ O₃ and 88% polybutylene terephthalate as inExample 1 /check example number!/ into test specimens for UL test 94.For comparison, a control mixture is used which is made in accordancewith the same formula, except that commercial octabromodiphenyl is usedas the flameproofing agent.

In UL fire resistance test 94, the mixture /containing compound/ cachieves the rating V0/V0, but with octabromodiphenyl only V1/V1. After14 days of heating at 150° C., the invention specimen has no coating ofany kind, but the control specimen has a perceptible white coating ofoctabromodiphenyl after only 7 days. If both specimens are heated eachin a long-necked glass flask at 1 Torr for 7 hours at 180° C., theinvention specimen remains unaltered, while in the colder parts of theglass flask containing the control specimen, crystals ofoctabromodiphenyl have settled; the weight loss after heating amounts to0.18% in the invention specimen, and in the control it is 1.2%.

EXAMPLE 53

83 weight % acrylnitrile-butadiene-styrene-copolymer[isate] are mixed ina two roller corn mill with 12 weight % poly-pentabromide-benzylacrylate(b) and 5 weight % Sb₂ O₃, the rolled sheet is crushed and molded byinjection [injectionmolded] into test substances for the fire testaccording to UL 94. The results of the fire test are V1/V1. Chalking outcannot be observed.

EXAMPLE 54

A copolymer of tetrabromo-p-xylylene glycol bisacrylate andtetrachloro-p-xylylene glycol bisacrylate, with a bromine content of 29wt.-% and a chlorine content of 17 wt.-% and having a melting pointabove 250° C., is added in the amount of 11 wt.-%, together with 5 wt.-%of antimony trioxide, to a commercial polybutylene terephthalate; themixture is made into chopped granules in a double screw extrudingmachine, and then injection molded to make test specimens for UL test94. The fire resistance rating is V0/VI; no chalking is perceived on thespecimens even after 7 days of heating at 150° C. 7 hours of heating at180° C. and 1 Torr produces a weight loss of only 0.14%.

EXAMPLE 55

The infusible polytetrabromoxylylene bisacrylate (PTA) named in Examplewas added in amounts of 12 wt.-%, together with 5 wt.-% of Sb₂ O₃ to

(a) commercial polypropylene

(b) commercial polystyrene.

The oxygen index (Ox.I.) values measured show a good and in some casessuperior effectiveness in comparison with the 0 value of the plasticscontaining no flameproofing agents, in accordance with the table below.

EXAMPLE 56

The polypentabromobenzyl acrylate (PPA) referred to in Example wasincorporated in amounts of 12 wt.-%, together with 5 wt.-% of antimonytrioxide, into

(a) Commercial polypropylene

(b) Commercial polyethylene

(c) Commercial ABS,

and was found to have good flame inhibiting action, in accordance withthe oxygen index in comparison with the 0 value.

    ______________________________________                                                                      Comparison                                                  Additive          Ox. I.                                          Ex.  Plastic      Kind   Amount Ox. I.                                                                              O value                                 ______________________________________                                        55 a Polypropylene                                                                              PTA    12     21.2  17.3                                    55 b Polystyrene  PTA    12     22.5  17.3                                    56 a Polypropylene                                                                              PPA    12     23.0  17.3                                    56 b Polyethylene PPA    12     27.0  18.5                                    56 c ABS          PPA    12     24.0  20.5                                    ______________________________________                                    

What is claimed is:
 1. A solid homopolymer of a monomer having theformula ##STR12## wherein n = 0 or 1, X is bromine or chlorine, R ishydrogen or methyl, said polymer having a molecular weight between 1 ×10³ and 10 × 10⁶, said molecular weight being determined by gelpermeation chromatography in tetrahydrofuran.
 2. A polymer according toclaim 1 wherein n =
 0. 3. A polymer according to claim 2 wherein X isbromine.
 4. A polymer according to claim 2 wherein X is a mixture ofbromine and chlorine.
 5. A polymer according to claim 2 which iscross-linked and infusible.
 6. A polymer according to claim 1 having amolecular weight between 5·10³ and 5·10⁶ determined by gel permeationchromatography in tetrahydrofuran.
 7. A polymer according to claim 1having on the phenyl radical 4-5 bromine atoms and 0 or 1 chlorineatoms.
 8. A polymer according to claim 1 having on the phenyl radical3-4 bromine atoms and 0-1 chlorine atoms.
 9. A polymer according toclaim 1 wherein said monomer has the formula ##STR13##
 10. A polymeraccording to claim 1 wherein said monomer has the formula ##STR14## 11.A polymer according to claim 1 wherein said monomer has the formula##STR15##
 12. A polymer according to claim 1 wherein said monomer ispentabromobenzylacrylate.
 13. A polymer according to claim 1 whereinsaid monomer is pentachlorobenzylacrylate.
 14. A polymer according toclaim 1 wherein said monomer is pentabromobenzylmethacrylate.
 15. Apolymer according to claim 1 wherein said monomer ispentachlorobenzylmethylacrylate.
 16. A polymer according to claim 1wherein n =
 1. 17. A polymer according to claim 16 wherein said polymeris thermoplastic and uncrosslinked.
 18. A polymer according to claim 17wherein said monomer is pentabromobenzyl acrylate.
 19. A polymeraccording to claim 17 wherein said monomer ispentabromobenzylmethacrylate.
 20. A process for preparing the polymer ofclaim 1 which comprises contacting a monomer of the formula ##STR16##wherein n = 0 or 1, X is bromine or chlorine, R is hydrogen or methylwith a radical polymerization catalyst under radical polymerizationreaction conditions.
 21. A process according to claim 20 wherein saidreaction conditions include a temperature of between 0° and 150° C. 22.A process according to claim 21 wherein the radical polymerizationcatalyst is an organic peroxide, an inorganic peroxide or an aliphaticazo compound.
 23. A process according to claim 22 wherein said radicalpolymerization catalyst is selected from the group consisting ofdibenzoyl peroxide, dicumyl peroxide, potassium peroxydisulfate andazodiisobutyric acid nitrile.
 24. A flame-retardant plastic compositioncomprising a normally flammable plastic and the polymer of claim
 1. 25.A flame-retardant plastic composition according to claim 24 wherein thepolymer of claim 1 contains 35 to 85% chlorine and/or bromine.
 26. Aflame-retardant plastic composition according to claim 24 wherein thepolymer of claim 1 is present in an amount 5 to 20 weight percent.
 27. Aflame-retardant plastic composition according to claim 26 wherein saidpolymer is present in said plastic composition in an amount of 7 to 12%by weight.